110 MR. 0. THOMAS ON RODENTS FROM PERU. [Jan. 17, 
above and beneath, uniformly thinly clad with brown hairs. Feet 
white, with a faint admixture of brown on the metacarpus and 
metatarsus. Foot-pads large and rounded, as in the typical Rhipi- 
domys. Fifth hind toes as in H. cinereus. Mammiee 6, one pectoral 
and two inguinal pairs. Ears without a projection on their anterior 
edge. Incisors and supraorbital margins as in H. cinereus. 
I have much pleasure in naming this peculiar species after Prof. 
Taczanowski, to whose kindness I am indebted for the opportunity 
of working out this interesting collection of mammals. H. tacz- 
anowskii may be readily distinguished from the last species by its 
much smaller size, aud from its other near ally, H. bicolor, Tomes, 
by the fact that that species hasa much shorter tail (3°5 in.), shorter 
hair, and a pure white belly. 
12. Hesprromys (HABROTHRIX) OLIVACEUS, Waterh. 
Mus (Habrothriz) olivaceus,Waterh. P. Z.S. 1837, p. 6. 
Hesperomys renggeri, Waterh. Zool. Voy. Beagle, ii. p. 57, p]. xv. 
(1839). 
a, 6. Tumbez, sea-level, June 1876. 
ce. Callacate, 4800’, April 1879. 
Head and Forearm Muzzle Ear-conch. 
body. Tail. Hind foot. and hand. toear. length. 
OiGissk teow 3°14 87 1°05 °93 63 
6.3 (imm.) 3°0 2°75 “86 1:0 "86 “60 
0. Ottessiemuel One 2°65 79 1:0 "94 “56 
This species seems to be a very common one all along the western 
parts of S. America ; for, in addition to these Peruvian examples, the 
Museum contains a considerable series of specimens from Bolivia 
and Chili, including the types of the species, collected by Mr. Dar- 
win during the voyage of the ‘ Beagle.’ Mr. Tomes also records it 
from Ecuador. 
It will seen by the dimensions given above that the Callacate spe- 
cimen has somewhat shorter ears, feet, and tail than the others, 
while it has a larger body and head ; and it has also rather thicker 
and softer fur. It seems very probable, however, that these differences 
are only owing to the much greater altitude at which it was obtained, 
since it is a well-known law among mammals that individuals from 
colder climates have a tendency to have larger bodies and shorter 
extremities than those of the same species living in warmer places. 
13, Hesperomys (HaBROTHRIX) CALIGINOSUS, Tomes, P. Z. S. 
1860, p. 263. 
a-f. Huambo, 3700', April and May 1880. 
Head and Forearm Ear-conch, Muzzle 
body. Tail. Hind foot, and hand. length. to ear. 
ag... AO 2°9 *84 1:07 "52 96 
bug.. 39 3°01 *85 — "51 °98 
cD 3°5 3°0 85 1°05 52 °92 
